1. Technical Field of the Invention
The invention relates to a printer having a controller for receiving print information and generating a command and an engine for executing print in accordance with the command, particular to a printer capable of transferring various types of information from the controller to the engine by the command in a short time, and a new communication protocol on a video interface between a the engine and the controller.
2. Related Art
FIG. 6 is a schematic drawing to show the electric configuration of a printer in a related art. A printer 1 is connected to a host computer 2 such as a personal computer and executes print based on a print command from the host computer 2. The printer 1 is roughly divided into an image processing controller 3 and an engine 4. When a command is issued from the host computer 2, first the image processing controller 3 receives print information and generates commands given to the engine 4 and image data to be printed based on the received print information.
As shown in FIG. 6, the engine 4 is roughly divided into a mechanical controller 5 for controlling a mechanical section 6 and this mechanical section 6. When the generated commands are issued from the image processing controller 3, the mechanical controller 5 receives the commands and controls parts of the mechanical section 6 in accordance with the commands for executing print. Usually, the engine 4 is constructed by a paper feed unit, a photo sensitive unit, a transfer unit, a fixing unit, a paper discharge unit, etc. Specifically, the mechanical controller 5 controls motors, clutches, sensors, etc., placed in the units.
As shown in FIG. 6, an interface section between the image processing controller 3 and the mechanical controller 5 is called a video interface section 7. The video interface section 7 usually comprises dedicated lines for transferring specific signals, such as a communication line for announcing mutual power stable state and a communication line for transmitting video data, and a serial communication line for transmitting the above-mentioned commands. On the serial communication line, each command is transmitted from the image processing controller 3 to the mechanical controller 5 and the mechanical controller 5 responds to the command with a status returned to the image processing controller 3. The status mainly indicates the state of the engine 4 and the image processing controller 3 grasps the state of the engine 4 based on the returned status.
In the printer in the related art, the serial communications are designed for returning a one-byte state in response to a one-byte command.
In the printer in the related art, particularly for monochrome print, the types of information transferred on the video interface section 7 are relatively small in number and selective information pieces are also small in number, so that main information is transferred over the dedicated lines and the serial communications are used for mainly transferring exceptional information such as error information. Therefore, the types of information are small in number and it is sufficient to provide one byte for a command and one byte for a status, as described above.
However, in a recent printer being capable of executing color print and having a wide variety of functions, the types of information to be sent from the image processing controller 3 to the mechanical controller 5 are also many and the number of selective information pieces also grows. It is preferable that a large number of types of information as mentioned are transferred with commands in serial communications without using the dedicated lines, but one-byte commands are not adequate for transferring a large number of types of information as mentioned. Therefore, if the communication architecture of the printer in the related art is not changed, it becomes necessary to transmit a one-byte command twice or more to transfer a piece of information, thereby increasing the communication time.
Further, in some sort of the recent printer using a laser beam, such as a page printer, the mechanical section in the engine has a photoconductive drum where a latent image is formed by a laser beam and charged toner is deposited and a transfer unit for superposing and transferring toner images formed on the photoconductive drum, wherein the superposed and transferred toner image on the transfer unit is transferred to a print medium such as print paper. For such printer capable of executing color print, various print modes such as monochrome print, color print, single-sided print, double-sided print, and sort output to a multi-bin unit have been required to be selected as desired. In such a large-scale electronic printer, much print information needs to be transferred between the image processing controller and a mechanical controller in a print engine. Thus, the transfer capacity of an interface needs to be increased; this results in an increase in costs. Therefore, optimizing the protocol of the interface is an indispensable requirement for increasing the print speed.